/* ----------------------------------------------------------------------
* Copyright (C) 2010-2014 ARM Limited. All rights reserved.
*
* $Date:        19. March 2015
* $Revision: 	V.1.4.5
*
* Project: 	    CMSIS DSP Library
* Title:	    arm_biquad_cascade_df1_q15.c
*
* Description:	Processing function for the
*				Q15 Biquad cascade DirectFormI(DF1) filter.
*
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*   - Redistributions of source code must retain the above copyright
*     notice, this list of conditions and the following disclaimer.
*   - Redistributions in binary form must reproduce the above copyright
*     notice, this list of conditions and the following disclaimer in
*     the documentation and/or other materials provided with the
*     distribution.
*   - Neither the name of ARM LIMITED nor the names of its contributors
*     may be used to endorse or promote products derived from this
*     software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
* -------------------------------------------------------------------- */

#include "arm_math.h"

/**
 * @ingroup groupFilters
 */

/**
 * @addtogroup BiquadCascadeDF1
 * @{
 */

/**
 * @brief Processing function for the Q15 Biquad cascade filter.
 * @param[in]  *S points to an instance of the Q15 Biquad cascade structure.
 * @param[in]  *pSrc points to the block of input data.
 * @param[out] *pDst points to the location where the output result is written.
 * @param[in]  blockSize number of samples to process per call.
 * @return none.
 *
 *
 * <b>Scaling and Overflow Behavior:</b>
 * \par
 * The function is implemented using a 64-bit internal accumulator.
 * Both coefficients and state variables are represented in 1.15 format and multiplications yield a 2.30 result.
 * The 2.30 intermediate results are accumulated in a 64-bit accumulator in 34.30 format.
 * There is no risk of internal overflow with this approach and the full precision of intermediate multiplications is preserved.
 * The accumulator is then shifted by <code>postShift</code> bits to truncate the result to 1.15 format by discarding the low 16 bits.
 * Finally, the result is saturated to 1.15 format.
 *
 * \par
 * Refer to the function <code>arm_biquad_cascade_df1_fast_q15()</code> for a faster but less precise implementation of this filter for Cortex-M3 and Cortex-M4.
 */

void arm_biquad_cascade_df1_q15(
    const arm_biquad_casd_df1_inst_q15 *S,
    q15_t *pSrc,
    q15_t *pDst,
    uint32_t blockSize)
{


#ifndef ARM_MATH_CM0_FAMILY

    /* Run the below code for Cortex-M4 and Cortex-M3 */

    q15_t *pIn = pSrc;                             /*  Source pointer                               */
    q15_t *pOut = pDst;                            /*  Destination pointer                          */
    q31_t in;                                      /*  Temporary variable to hold input value       */
    q31_t out;                                     /*  Temporary variable to hold output value      */
    q31_t b0;                                      /*  Temporary variable to hold bo value          */
    q31_t b1, a1;                                  /*  Filter coefficients                          */
    q31_t state_in, state_out;                     /*  Filter state variables                       */
    q31_t acc_l, acc_h;
    q63_t acc;                                     /*  Accumulator                                  */
    int32_t lShift = (15 - (int32_t) S->postShift);       /*  Post shift                                   */
    q15_t *pState = S->pState;                     /*  State pointer                                */
    q15_t *pCoeffs = S->pCoeffs;                   /*  Coefficient pointer                          */
    uint32_t sample, stage = (uint32_t) S->numStages;     /*  Stage loop counter                           */
    int32_t uShift = (32 - lShift);

    do
    {
        /* Read the b0 and 0 coefficients using SIMD  */
        b0 = *__SIMD32(pCoeffs)++;

        /* Read the b1 and b2 coefficients using SIMD */
        b1 = *__SIMD32(pCoeffs)++;

        /* Read the a1 and a2 coefficients using SIMD */
        a1 = *__SIMD32(pCoeffs)++;

        /* Read the input state values from the state buffer:  x[n-1], x[n-2] */
        state_in = *__SIMD32(pState)++;

        /* Read the output state values from the state buffer:  y[n-1], y[n-2] */
        state_out = *__SIMD32(pState)--;

        /* Apply loop unrolling and compute 2 output values simultaneously. */
        /*      The variable acc hold output values that are being computed:
         *
         *    acc =  b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2]
         *    acc =  b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2]
         */
        sample = blockSize >> 1u;

        /* First part of the processing with loop unrolling.  Compute 2 outputs at a time.
         ** a second loop below computes the remaining 1 sample. */
        while(sample > 0u)
        {

            /* Read the input */
            in = *__SIMD32(pIn)++;

            /* out =  b0 * x[n] + 0 * 0 */
            out = __SMUAD(b0, in);

            /* acc +=  b1 * x[n-1] +  b2 * x[n-2] + out */
            acc = __SMLALD(b1, state_in, out);
            /* acc +=  a1 * y[n-1] +  a2 * y[n-2] */
            acc = __SMLALD(a1, state_out, acc);

            /* The result is converted from 3.29 to 1.31 if postShift = 1, and then saturation is applied */
            /* Calc lower part of acc */
            acc_l = acc & 0xffffffff;

            /* Calc upper part of acc */
            acc_h = (acc >> 32) & 0xffffffff;

            /* Apply shift for lower part of acc and upper part of acc */
            out = (uint32_t) acc_l >> lShift | acc_h << uShift;

            out = __SSAT(out, 16);

            /* Every time after the output is computed state should be updated. */
            /* The states should be updated as:  */
            /* Xn2 = Xn1    */
            /* Xn1 = Xn     */
            /* Yn2 = Yn1    */
            /* Yn1 = acc   */
            /* x[n-N], x[n-N-1] are packed together to make state_in of type q31 */
            /* y[n-N], y[n-N-1] are packed together to make state_out of type q31 */

#ifndef  ARM_MATH_BIG_ENDIAN

            state_in = __PKHBT(in, state_in, 16);
            state_out = __PKHBT(out, state_out, 16);

#else

            state_in = __PKHBT(state_in >> 16, (in >> 16), 16);
            state_out = __PKHBT(state_out >> 16, (out), 16);

#endif /*      #ifndef  ARM_MATH_BIG_ENDIAN    */

            /* out =  b0 * x[n] + 0 * 0 */
            out = __SMUADX(b0, in);
            /* acc +=  b1 * x[n-1] +  b2 * x[n-2] + out */
            acc = __SMLALD(b1, state_in, out);
            /* acc +=  a1 * y[n-1] + a2 * y[n-2] */
            acc = __SMLALD(a1, state_out, acc);

            /* The result is converted from 3.29 to 1.31 if postShift = 1, and then saturation is applied */
            /* Calc lower part of acc */
            acc_l = acc & 0xffffffff;

            /* Calc upper part of acc */
            acc_h = (acc >> 32) & 0xffffffff;

            /* Apply shift for lower part of acc and upper part of acc */
            out = (uint32_t) acc_l >> lShift | acc_h << uShift;

            out = __SSAT(out, 16);

            /* Store the output in the destination buffer. */

#ifndef  ARM_MATH_BIG_ENDIAN

            *__SIMD32(pOut)++ = __PKHBT(state_out, out, 16);

#else

            *__SIMD32(pOut)++ = __PKHBT(out, state_out >> 16, 16);

#endif /*      #ifndef  ARM_MATH_BIG_ENDIAN    */

            /* Every time after the output is computed state should be updated. */
            /* The states should be updated as:  */
            /* Xn2 = Xn1    */
            /* Xn1 = Xn     */
            /* Yn2 = Yn1    */
            /* Yn1 = acc   */
            /* x[n-N], x[n-N-1] are packed together to make state_in of type q31 */
            /* y[n-N], y[n-N-1] are packed together to make state_out of type q31 */
#ifndef  ARM_MATH_BIG_ENDIAN

            state_in = __PKHBT(in >> 16, state_in, 16);
            state_out = __PKHBT(out, state_out, 16);

#else

            state_in = __PKHBT(state_in >> 16, in, 16);
            state_out = __PKHBT(state_out >> 16, out, 16);

#endif /*      #ifndef  ARM_MATH_BIG_ENDIAN    */


            /* Decrement the loop counter */
            sample--;

        }

        /* If the blockSize is not a multiple of 2, compute any remaining output samples here.
         ** No loop unrolling is used. */

        if((blockSize & 0x1u) != 0u)
        {
            /* Read the input */
            in = *pIn++;

            /* out =  b0 * x[n] + 0 * 0 */

#ifndef  ARM_MATH_BIG_ENDIAN

            out = __SMUAD(b0, in);

#else

            out = __SMUADX(b0, in);

#endif /*      #ifndef  ARM_MATH_BIG_ENDIAN    */

            /* acc =  b1 * x[n-1] + b2 * x[n-2] + out */
            acc = __SMLALD(b1, state_in, out);
            /* acc +=  a1 * y[n-1] + a2 * y[n-2] */
            acc = __SMLALD(a1, state_out, acc);

            /* The result is converted from 3.29 to 1.31 if postShift = 1, and then saturation is applied */
            /* Calc lower part of acc */
            acc_l = acc & 0xffffffff;

            /* Calc upper part of acc */
            acc_h = (acc >> 32) & 0xffffffff;

            /* Apply shift for lower part of acc and upper part of acc */
            out = (uint32_t) acc_l >> lShift | acc_h << uShift;

            out = __SSAT(out, 16);

            /* Store the output in the destination buffer. */
            *pOut++ = (q15_t) out;

            /* Every time after the output is computed state should be updated. */
            /* The states should be updated as:  */
            /* Xn2 = Xn1    */
            /* Xn1 = Xn     */
            /* Yn2 = Yn1    */
            /* Yn1 = acc   */
            /* x[n-N], x[n-N-1] are packed together to make state_in of type q31 */
            /* y[n-N], y[n-N-1] are packed together to make state_out of type q31 */

#ifndef  ARM_MATH_BIG_ENDIAN

            state_in = __PKHBT(in, state_in, 16);
            state_out = __PKHBT(out, state_out, 16);

#else

            state_in = __PKHBT(state_in >> 16, in, 16);
            state_out = __PKHBT(state_out >> 16, out, 16);

#endif /*   #ifndef  ARM_MATH_BIG_ENDIAN    */

        }

        /*  The first stage goes from the input wire to the output wire.  */
        /*  Subsequent numStages occur in-place in the output wire  */
        pIn = pDst;

        /* Reset the output pointer */
        pOut = pDst;

        /*  Store the updated state variables back into the state array */
        *__SIMD32(pState)++ = state_in;
        *__SIMD32(pState)++ = state_out;


        /* Decrement the loop counter */
        stage--;

    }
    while(stage > 0u);

#else

    /* Run the below code for Cortex-M0 */

    q15_t *pIn = pSrc;                             /*  Source pointer                               */
    q15_t *pOut = pDst;                            /*  Destination pointer                          */
    q15_t b0, b1, b2, a1, a2;                      /*  Filter coefficients           */
    q15_t Xn1, Xn2, Yn1, Yn2;                      /*  Filter state variables        */
    q15_t Xn;                                      /*  temporary input               */
    q63_t acc;                                     /*  Accumulator                                  */
    int32_t shift = (15 - (int32_t) S->postShift); /*  Post shift                                   */
    q15_t *pState = S->pState;                     /*  State pointer                                */
    q15_t *pCoeffs = S->pCoeffs;                   /*  Coefficient pointer                          */
    uint32_t sample, stage = (uint32_t) S->numStages;     /*  Stage loop counter                           */

    do
    {
        /* Reading the coefficients */
        b0 = *pCoeffs++;
        pCoeffs++;  // skip the 0 coefficient
        b1 = *pCoeffs++;
        b2 = *pCoeffs++;
        a1 = *pCoeffs++;
        a2 = *pCoeffs++;

        /* Reading the state values */
        Xn1 = pState[0];
        Xn2 = pState[1];
        Yn1 = pState[2];
        Yn2 = pState[3];

        /*      The variables acc holds the output value that is computed:
         *    acc =  b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2]
         */

        sample = blockSize;

        while(sample > 0u)
        {
            /* Read the input */
            Xn = *pIn++;

            /* acc =  b0 * x[n] + b1 * x[n-1] + b2 * x[n-2] + a1 * y[n-1] + a2 * y[n-2] */
            /* acc =  b0 * x[n] */
            acc = (q31_t) b0 * Xn;

            /* acc +=  b1 * x[n-1] */
            acc += (q31_t) b1 * Xn1;
            /* acc +=  b[2] * x[n-2] */
            acc += (q31_t) b2 * Xn2;
            /* acc +=  a1 * y[n-1] */
            acc += (q31_t) a1 * Yn1;
            /* acc +=  a2 * y[n-2] */
            acc += (q31_t) a2 * Yn2;

            /* The result is converted to 1.31  */
            acc = __SSAT((acc >> shift), 16);

            /* Every time after the output is computed state should be updated. */
            /* The states should be updated as:  */
            /* Xn2 = Xn1    */
            /* Xn1 = Xn     */
            /* Yn2 = Yn1    */
            /* Yn1 = acc    */
            Xn2 = Xn1;
            Xn1 = Xn;
            Yn2 = Yn1;
            Yn1 = (q15_t) acc;

            /* Store the output in the destination buffer. */
            *pOut++ = (q15_t) acc;

            /* decrement the loop counter */
            sample--;
        }

        /*  The first stage goes from the input buffer to the output buffer. */
        /*  Subsequent stages occur in-place in the output buffer */
        pIn = pDst;

        /* Reset to destination pointer */
        pOut = pDst;

        /*  Store the updated state variables back into the pState array */
        *pState++ = Xn1;
        *pState++ = Xn2;
        *pState++ = Yn1;
        *pState++ = Yn2;

    }
    while(--stage);

#endif /*     #ifndef ARM_MATH_CM0_FAMILY */

}


/**
 * @} end of BiquadCascadeDF1 group
 */
